Polyolefin resins are widely used as various shaped articles owing to their low cost and excellent physical properties. However, in the case of polypropylene, for example, there has been a problem such that various kinds of shaping defects have been generated in vacuum forming, blow molding, foam molding, extrusion molding, or calendering because melt tension of polypropylene at the time of shaping is low.
An attempt for raising melt tension of polypropylene by increasing a molecular weight of polypropylene has been carried out so as to improve such shaping processability as mentioned above, but there has been a problem such that a preferable balance between melt tension and melt fluidity cannot be obtained attributed to lowering of melt fluidity, as one of the indices of shaping processability, caused by the molecular weight increase.
As a method for improving shaping processability of polyolefin resins, there have been proposed methods of adding an alkyl(meth)acrylate polymer having a long chain alkyl group to the polyolefin resins (Patent Documents 1 and 2). In Patent Document 1, lauryl methacrylate polymer is used as the alkyl(meth)acrylate polymer, and in Patent Document 2, stearyl methacrylate copolymer is used as the alkyl(meth)acrylate polymer.
However, there is a case where handling properties, as an additive, of the alkyl (meth)acrylate polymer having a long chain alkyl group become a problem because it is difficult to recover the alkyl(meth)acrylate polymer as a powder owing to its low glass transition temperature. Moreover, there is a case where a homogeneous resin composition cannot be obtained because it is difficult to homogeneously disperse the alkyl(meth)acrylate polymer in polyolefin resins.
In addition, a method of adding a processing aid containing polytetrafluoroethylene to the polyolefin resins has been proposed (Patent Document 3). However, there has been a need for dehalogenation depending on a use of the polyolefin resins, and hence a halogen-free processing aid for the polyolefin resins has been strongly desired.
Patent Document 1: Japanese Patent Application Laid-Open No. Hei 9-255,816
Patent Document 2: Japanese Patent Application Laid-Open No. Hei 8-302,098
Patent Document 3: Japanese Patent Application Laid-Open No. Hei 11-124,478